System Design · Senior · Question 63 of 75
Why do payment systems use an append-only double-entry ledger instead of a mutable balance column?
- ✓Correct answer: Every movement is recorded as balanced debit/credit entries, giving an auditable history and making balances derivable and verifiable
- 2It uses less storage
- 3It's required by SQL
Explanation
Corrections are new entries, not edits. A cached balance can be recomputed from the ledger.